The present invention relates to a process for preparing a cyclic ketone having from 7 to 16 carbon atoms, which comprises at least the oxidation of a composition (I) comprising at least one cyclic alkene which has from 7 to 16 carbon atoms and at least one C—C double bond by means of dinitrogen monoxide to give a composition (A), treatment of the composition (A) with at least one base to give a composition (B), hydrogenation of the composition (B) in the presence of at least one catalyst to give a composition (C) and purification of the composition (C), comprising at least a thermal treatment of the composition (C) with at least one acid or at least one catalyst comprising at least one transition metal, and further purification by a method selected from the group consisting of distillation, extraction and crystallization.
The oxidation of an olefinic compound by means of dinitrogen monoxide to form an aldehyde or a ketone is described, for example, in GB 649,680 or the equivalent U.S. Pat. No. 2,636,898. In both documents, it is disclosed in general terms that the oxidation can in principle be carried out in the presence of a suitable oxidation catalyst. The more recent scientific articles by G. I. Panov et al., “Non-Catalytic Liquid Phase Oxidation of Olefines with Nitrous Oxide. 1. Oxidation of Cyclohexene to Cyclohexanone”, React. Kinet. Catal. Left. Vol. 76, No. 2 (2002) pp. 401-405, and K. A. Dubkov et al., “Non-Catalytic Liquid Phase Oxidation of Olefines with Nitrous Oxide. 2. Oxidation of Cyclopentene to Cyclopentanone”, React. Kinet. Catal. Left. Vol. 77, No. 1 (2002) pp. 197-205, likewise describe oxidations of olefinic compounds by means of dinitrogen monoxide. A scientific article “Liquid Phase Oxidation of Olefines with Nitrous Oxide to Carbonyl Compounds” by E. V. Starokon et al. in Adv. Synth. Catal. 2004, 346, 268-274, also reports a mechanistic study of the oxidation of olefins by means of dinitrogen monoxide in the liquid phase.
The synthesis of carbonyl compounds from olefins using dinitrogen monoxide is also described in various international patent applications. Thus, WO 03/078370 discloses a process for preparing carbonyl compounds from aliphatic olefins using dinitrogen monoxide. The reaction is carried out at temperatures in the range from 20 to 350° C. and pressures of from 0.01 to 100 atm. WO 03/078374 discloses a corresponding process for preparing cyclohexanone. According to WO 03/078372, cyclic ketones having from 4 to 5 carbon atoms are prepared. According to WO 03/078375, cyclic ketones are prepared from cyclic olefins having from 7 to 20 carbon atoms under these process conditions. WO 03/078371 discloses a process for preparing substituted ketones from substituted olefins. WO 04/000777 discloses a process for reacting diolefins and polyolefins with dinitrogen monoxide to form the corresponding carbonyl compounds.
WO 2005/030690 and WO 2005/030689 describe processes for preparing cyclododecanone, in which an oxidation by means of dinitrogen monoxide is carried out in one process step. WO 2005/030690 describes a process for preparing cyclododecanone by oxidation of 1,5,9-cyclododecatriene (CDT) by means of N2O to form cyclododeca-4,8-dienone and subsequent hydrogenation of cyclododeca-4,8-dienone to give cyclododecanone.
As an alternative, cyclododecanone, for example, is prepared, for example, by air oxidation of cyclododecane in the presence of boric acid to form cyclododecyl borate, hydrolysis of the borate to cyclododecanol and subsequent dehydrogenation of the cyclododecanol. Cyclododecane itself is obtained by complete hydrogenation of cyclododecatriene. A description of this industrial process for the synthesis of cyclododecanone may be found, inter alia, in T. Schiffer, G. Oenbrink, “Cyclododecanol, Cyclododecanon and Laurolactam” in Ullmann's Encyclopedia of Industrial Chemistry, 6th Edition, 2000, Electronic Release, Wiley VCH.
A further process starts out from the epoxidation of cyclododecatriene, with cyclododecanone being obtained from the epoxide after hydrogenation and rearrangement. Such a process is described, for example, in EP 1 018 498 A2.
DE 103 44 595 A and DE 103 44 594 A describe processes for preparing cyclododecanone, in which an oxidation by means of dinitrogen monoxide is carried out in one process step.
In all processes, the purity of the crude products without additional purification is not sufficient for some applications. Organic compounds having oxygen-comprising groups, in particular, are frequently still comprised in the products obtained in excessively large amounts.
In the oxidation of olefins by means of dinitrogen monoxide, it is possible for, for example, aidehydes to be formed as by-products, as described, for example, in Panov et al., Adv. Synth. Catal. (2004) 346, 268-274.
This is problematical insofar as cyclic ketones are required in high purity for various applications. Thus, for example, cyclododecanone is an important intermediate in the preparation of, for example, laurolactam, dodecanedicarboxylic acid and polyamides derived therefrom, for example Nylon 12 or Nylon 6.12. The impurities such as aidehydes comprised in the cyclic ketones can be removed only with difficulty by conventional purification methods such as distillation, extraction or recrystallization, since the functional groups and the number of carbon atoms are similar. For this reason, a very complicated purification, for example by multistage distillation or crystallization, is necessary in these cases. These purification methods are therefore complicated and costly.